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Gustav Spörer (1822–1895)

Gustav Spörer was born in Berlin on 23 October 1822. Between 1840 and 1843 he studied mathematics and astronomy at the University of Berlin. He started his professional career as a school teacher, and only began his solar observations at age 36, and with very modest equipment.

Spörer shares credit with the Englishman R. C. Carrington for independent and nearly simultaneous discoveries of two solar features of great importance. By the early 1860s, both astronomers had accumulated sunspot observations demonstrating:

The differential rotation of the Sun's surface, as inferred from the apparent EW motion of sunspots, and

The gradual equatorward drift of sunspots in the course of the sunspot cycle (now often called Spörer's Law).

With his reputation now established, Spörer was invited in 1874 to join the Potsdam Astrophysical Observatory, then still under construction, where he became chief observer in 1882. At Potsdam, he continued his solar observing program and became engaged in historical researches into 17th century sunspot observations. By 1887 Spörer had convinced himself that the Sun was behaving unusually in the 17th century, with very few sunspots present on its surface. Through careful analyses of extant 17th century observational material, he compiled a list of the few sunspots observed during that time period. Surprisingly, this groundbreaking work attracted relatively little attention until it was publicized by E. W. Maunder as part of his own historical studies of 17th century sunspot observations.

Spörer retired from Potsdam on 1 October 1894. Despite having enjoyed perfect health throughout his life, he died suddenly on 7 July 1895.

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